1. Field of the Invention
This invention relates to a machine for bending a small-diameter metallic conduit at several points and more particularly, to a small-diameter metallic conduit bending machine adapted to shape a metallic conduit whose individual bend portions differ in the bend direction three-dimensionally from one another, not lying on the same plane, such as the fuel pipeline or brake pipeline of a car.
2. Description of the Prior Art
A conventional bending machine of the foregoing type includes a required number of bending units disposed correspondingly to a plurality of bend portions, each unit being configured as shown in FIG. 12 so that with respect to each bending process, a receiving roll 21 is moved by a cylinder 22 to come into contact with a metallic conduit 23, and then a bending roll 24 is moved by a cylinder 25 to bend the metallic conduit 23. In the drawing, 26 and 27 are mounts, 28 and 29 are stays, and 30 is a basement.
According to the foregoing conventional bending machine, however, since the bending process is carried out by moving the receiving roll 21 and the bending roll 24 by means of the respective cylinders 22 and 25, one bending process needs two actions; thus, the processing time is long. Since the bending process is completed when the piston rods of both cylinders 22 and 25 are in an extended state, upon supply of a pressurized fluid into the cylinder (generally, an air cylinder) at the time of bending, the bending moment imposed on the piston rod increases, and flexure resulting from the reaction caused at the time of bending appears in the stays 28 and 29 and mounts 26 and 27 for supporting the cylinders 22 and 25; as a result, a minute discrepancy (called "breathing" by those skilled in the art) appears between the receiving roll 21 and the bending roll 24, thereby resulting in variations in products. To eliminate such a discrepancy, it is necessary to make the stays 28 and 29 and the mounts 26 and 27 thick and rigid; consequently, the machine becomes large in size and heavy (but, in spite of such provisions, some discrepancy cannot be eliminated). Further, since the whole machine is designed and composed while giving consideration to the position, orientation, etc. of each of the cylinders 22 and 25, receiving roll 21 and bending roll 24, a long time is needed for manufacture, such as assembly and adjustment; as a result, the machine cannot be put in service in time where the start of mass production is settled. In addition, since the number of parts and of moving portions is large, the manufacturing cost is very high and the durability is inferior.
Especially, where one bending mechanism and a subsequent bending mechanism are to be disposed close to each other, the two mechanisms cannot be disposed or must be mounted using a complicated mechanism because they would interfere with each other even partly. Further, when the metallic conduit is brandished during bending, it under movement tends to interfere with the bending member.